Method for air-conditioning a plurality of rooms



United States Patent 3,360,031 METHOD FOR AIR-CONDITIONING A PLURALITY OF ROOMS Sigvard Matts, Farsta, and Lars-Owe Grudeborn, Jonkoping, Sweden, assignors to Akfiebolaget Svenska Flaktfabriken, Stockholm, Sweden Filed Dec. 28, 1964, Ser. No. 422,882

Claims priority, application Sweden, Dec. 27, 1963,

12,297/ 63 8 Claims. (Cl. 165-2) ABSTRACT OF THE DISCLOSURE An air conditioning system consisting of a central conditioner for supplying conditioned primary air to each of a plurality of rooms, and individual room units for intermixing with said primary air, secondary air from the rooms, the temperature of the secondary air being reduced by a liquid heat exchange medium prior to mixing with the primary air in the room unit. The temperature of the liquid heat exchange medium is maintained within a specified range either by adding hot or cold medium or by heat exchange with the primary air in the central conditioning unit.

The present invention relates to a method for air-conditioning a plurality of rooms by means of air delivered from one or more central air-conditioning apparatus, which air is transported to and distributed into induction units in the various rooms as primary air in a quantity substantially corresponding to the need of ventilation and which by ejection effect induces and is intermixed with a certain quantity of local or secondary air. In the induction units the temperature of the secondary air before its mixing with the primary air is regulated in heat exchangers disposed in the induction units.

The buildings, which were erected only a few years ago, Were constructed in a very traditional manner, i.e. the outer walls were most often supporting parts and consisted of heavy material, for instance bricks. The window surface of the fronts was small, often not more than 15% of the total front surface. The inner walls were made as supporting walls with, for instance, bricks or hollow concrete blocks, and the floorings were made relatively strong. This resulted in that the heat which in one way or another was supplied to the buildings not used to make up the transmission losses was stored in the building material. In the heating season, the heat-storing capacity of the buildings could often be sufficiently great that no additional heat for nightly heating was necessary. In the cooling season, the air-conditioning plants of the buildings were most often started early in the morning or Wereif necessaryin operation all night long in order to utilize the cooler night-air and in this way to cool down the buildings to a suitable working temperature during daytime.

If this procedure is practised in a building which has been constructed according to modern building methods, it will be found that the heat-storing capacity is small, i.e. the temperature decrease and the temperature increase respectively will take place very rapidly and effectively. Materials which have a capacity to store heat to an extent worth mentioning are nowadays only used to a small extent. The buildings are constructed with fronts having a large glass surface (up to about 50% glass surface being not unusual today), light front element's, light inner walls, thin concrete floorings, and so forth.

The self-regulating ability of old buildings, i.e. their ability to store and give off heat respectively to a great extent, must therefore in modern buildings be replaced by a careful temperature regulation. To avoid this draw- 3,360,031 Patented Dec. 26, 1967 back, it has been the practice to utilize to a great extent the principle of limiting the distributed air quantity to a value necessary for the need of ventilation, and furthermore, the heat control of the room has been effected by means of heat exchangers disposed in each room, which heat exchangers during warm weather (summertime) were fed with cold water and through which the roomair was caused to pass by ejection effect while utilizing the energy of the ventilating air (the primary air). Such a system is described for instance in the US. Patent No. 2,363,294. During cold weather (wintertime) the heat exchangers were fed with warm water, whereby the heat losses by transmission through the outer walls of the room were made up. A desired individual regulation of the room temperature has been possible by controlling the capacity of the heat exchangers (either by varying the circulating water quantity of the air quantity passing through the heat exchangers).

By varying the water temperature in the heat exchangers in accordance with the outdoor condition and the season, as hitherto has been done, a desired increase of the room temperature has required an increase of the capacity of the heat exchangers when these were fed with warm water, and a decrease of the capacity when they were fed with cold water.

A disadvantage of this system is that if a person in any room wants to increase or decrease the temperature of the supplied air, he is not able to know beforehand in which direction the control knob for the capacity regulation is to be turned in order to obtain a desired result, as he does not know, of a heating or a cooling medium at the moment is passing through the system.

Another disadvantage is that the size of the range of available regulation is dependent on the temperature difference between the water in the heat exchangers and the room air and, in the case when the water temperature has become equal to the room temperature, the possibility for adjustment is non-existent.

The invention, the object of which is to eliminate the above-mentioned disadvantages, is characterized in th-at irrespective of the outdoor condition and the season (temperature and sun)the liquid medium, normally water, supplied to the heat exchangers of the induction unitsis maintained at a temperature common for substantially the whole plant and being lower than the temperature of the secondary air. The temperature of the primary air is regulated in accordance with the outdoor condition (temperature and sun). By maintaining the Water supplied to the heat exchangers at a temperature, which is permanently considerably low-er than that of the roomair, an adjustment of the control knob in a certain direction always gives one and the same effect on the room temperature as a large range of regulation always is available.

Another advantage is that no so-called zone division of the circulating system for the liquid medium has been necessary to accommodate the temperature of the medium to the orientation of the different parts of the building with respect to the points of the compass and sun conditions.

For supplying to the rooms during wintertime the heat quantity necessary for the heating, the ventilating air (the primary air) can suitably be supplied with an overtemperature in accordance with the outdoor conditions (temperature and sun radiation). When operating under these conditions, in order to eliminate the loss of energy, which a simultaneous cooling with the medium and a heating with the air would give rise to, the circulating water may according to a suitable embodiment be utilized for a central pre-heating of the primary air. This is performed by conducting the medium heated in the heat exchangers of the induction units through one or more heat exchangers included in the central air-conditioning apparatus, through which heat exchanger(s) the primary air is taken in.

To prevent condensation of the moisture from the room-air on the heat exchangers of the induction units, the medium supplied to these heat exchangers should be maintained at a temperature, which is not substantially below the dew-point temperature of the room-air (the secondary air). This is accomplished by introducing, when required, a suitable quantity of heat from a separate heat source into the closed circulation circuit, of the liquid heat-exchange medium.

Upon an increase of the outdoor temperature, in order to maintain the difference between the temperature of the medium supplied to the heat exchangers of the induction units and the room temperature great enough to secure the desired available range of regulation a suitable heat quantity is removed from the closed circulation circuit of the liquid heat-exchange medium by a separate cooling device.

The above-mentioned governing of the temperature of the heat-exchange medium may suitably be obtained by adding a suitable quantity of Warm or cold medium. In order to secure the "best possible running economy, according to the invention the heated medium is supplied to the circuit at a supply point located in the return pipe from the induction units and before the heat exchanger(s) located in the central apparatus simultaneously as a corresponding medium quantity is discharged from the circuit at a point located in the return pipe from the induction units upstream of the above-mentioned supply point. On the other hand, the cooled medium is supplied to the circuit at a supply point located in the supply pipe to the induction units simultaneously as a corresponding medium quantity is discharged from the circuit at a point located in the supply pipe to the induction units upstream of the last-mentioned supply point.

The advantage of pre-heating the incoming primary air while simultaneously cooling the return medium from the heat exchangers of the induction units by the heat exchanger(s) disposed in the central apparatus is no longer available when the outdoor temperature is equal to or higher than the temperature of the circulating medium. In such cases it is desirable to re-circulate the medium coming from the induction units by by-passing the medium immediately to the induction units without first conducting the medium through the heat exchanger( s) in the central air-conditioning apparatus.

A suitable embodiment of the invention is characterized in that the heat exchanger(s) in the central airconditioning apparatus in certain cases (during summer) is (are) utilized for cooling and dehumidifying the ventilating air (the primary air).

The invention will now be closer described with reference to the accompanying drawing, showing in FIGS. 1 to inclusive a number of exemplifying embodiments of a plant, wherein the invented method is used.

In the drawing, each figure illustrates an air conditioning plant for buildings having a number of heat exchangers 1 included in the induction units of the plant and a heat exchanger 2 belonging to the central air conditioning apparatus of the plant (not shown) which regulates the temperature of the ventilating primary in ac cordance with the outside conditions, as influenced by the temperature and sun. 3 designates a pipe line which together with the members 1 and 2 constitutes a closed circulation circuit for a liquid medium. In the circuit is also included a circulation pump 4. 5 designates a flow of ventilating air through the heat exchanger 2 for a central pre-heating of same. In FIG. 2 there is illustrated an arrangement for maintaining a constant liquid flow through the heat exchanger 2 by means of a separate pump 6 and aby-pass line 7-irrespective of the fact if one or more of the heat exchangers 1 should be entirely or partly shut-off. In FIG. 3 there is shown an arrangement by means of which a suitable quantity of warm medium from a separate heat source (not shown in the drawing) is added to the circulation circuit at 8 simultaneously as a corresponding quantity medium is discharged at 9-in order to maintain the medium supplied to the heat exchangers at a temperature not substantially below the dew-point-temperature of the room-air. The control is eifected in a conventional manner by means of a thermostat 19 and a regulating valve 11. In FIG. 4 there is shown an arrangement by means of which a suitable quantity cold medium from a separate liquid cooler (not shown in the drawing) is added to the circulation circuit at 12 simultaneously as a corresponding medium quantity is discharged at 13-for the purpose of maintaining the medium supplied to the heat exchangers 1 at a pre-determined temperature lower than the temperature of the room-air. This control is effected in a conventional manner by means of a thermostat 14 and a regulating valve 15. As is evident from the two last mentioned figures the heated medium (FIG. 3) is supplied to the circuit at a supply point located in the return pipe line from the heat exchangers 1 upstream of the heat exchanger 2 simultaneously as a corresponding medium quantity is discharged from the circuit at a point located in the return pipe line from the heat exchangers 1 upstream of the above mentioned supply point, while according to the case illustrated in FIG. 4 the cooled medium is supplied to the circuit at a supply point located in the supply pipe line to the heat exchangers 1, simultaneously as a corresponding medium quantity is discharged from the circuit at a point located in the supply pipe line to the heat exchangers 1 upstream of the last mentioned supply point.

In cases when the ventilating air 5 passing through the heat exchanger 2 has a too high temperature to be able to cool the medium coming from the heat exchangers 1 (which temperature is sensed by a thermostat 20) the medium supplied to the heat exchangers 1 is maintained at intended temperature solely by means of the cooled medium supplied at 15. In this case of operation the ventilating air 5 ought to be cooled and dehumidified centrally-independent of the temperature conditions in the heat exchangers 1. According to FIG. 5 this can be performed by means of a three-way valve 16, governed by the above mentioned thermostat 20, and a by-pass line 17 by means of which the circulation circuit 3 can be divided into two separate circuits 3a and 3b with a common discharge at 18. In FIG. 5 19 designates a supply pipe line for the supply of cold medium to the circuit 3b. This supply is regulated by means of a valve 21 being governed by a thermostat 22 located in the air flow 5 coming from the heat exchanger 2. In this case the heat exchanger 2 functions as a cooling means for the ventilating air, which may effect dehumidification thereof. This system is effective during the summer season when the plant operates to cool the building.

What we claim is:

1. In a method for air-conditioning a plurality of rooms by means of air delivered from central air-conditioning apparatus, which air is transported to and distributed into the various rooms as primary air and which by ejection eiiect, induces and is intermixed with a quantity of local secondary air in at least one induction unit located in each room, in which unit the temperature of the secondary air before its mixing with the primary air is treated in heatexchangers disposed in the induction unit having liquid heat-exchange medium supplied thereto, the liquid medium supplied to the exchanger of the induction units, irrespective of the outdoor condition and the season, being at a temperature common for substantially the Whole plant, the temperature of the primary air being regulated in accordance with the outdoor condition; the improvement wherein said common temperature of the liquid heat exchange medium is controlled to remain in a range below the temperature of the secondary air, but not substantially below the dew-point temperature of the secondary air, the liquid medium thereby absorbing heat from the secondary air without causing condensation in the heat exchangers.

2. A method according to claim 1 wherein said central apparatus includes a central heat-exchanger and the liquid medium passing through the heat-exchangers of the induction units is caused to circulate in a closed circuit including said central heat-exchanger to thereby give 01f in said central heat-exchanger the heat absorbed in the room.

3. A method according to claim 2 wherein the heat given oil by the circulating liquid medium is utilized for a central preheating of the primary air.

4. A method according to claim 3 wherein said common temperature is caused to remain in said range by introducing a suitable quantity of heat from a separate heat source into the closed circulation circuit.

5. A method according to claim 3 wherein the medium supplied to the induction units is caused to remain in said range by removing from the closed circulation circuit a suitable quantity of heat.

6. A method according to claim 2 in which said com mon temperature is maintained by selectively adding suitable quantities of heated and cooled medium, wherein the heated medium is suppiled to the circuit at a first supply point located in the circuit downstream from the induction units and upstream of the central heat-exchanger and a corresponding quantity of medium is discharged from the circuit at a point located downstream from the induction units and upstream of said first supply point; and the cooled medium is supplied to the circuit at a second supply point located in the circuit downstream from the central heat-exchanger and upstream of the induction units and a corresponding quantity of medium is discharged from the circuit at a point located in the circuit downstream of the central exchanger and upstream of said second supply point.

7. A method according to claim 6 wherein the medium coming from the induction unit is recirculated by bypassing said medium immediately to the induction units without conducting said medium through the central heatexchanger.

8. A method according to claim 7 wherein the central. heat-exchanger during the cooling season is utilized for cooling or dehumidifying the primary air.

References Cited UNITED STATES PATENTS 2,930,593 3/1960 Blum -22 ROBERT A. OLEARY, Primary Examiner. CHARLES SUKALO, Examiner. 

1. IN A METHOD FOR AIR-CONDITIONING A PLURALITY OF ROOMS BY MEANS OF AIR DELIVERED FROM CENTRAL AIR-CONDITIONING APPARATUS, WHICH AIR IS TRANSPORTED TO AND DISTRIBUTED INTO THE VARIOUS ROOMS AS PRIMARY AIR AND WHICH BY EJECTION EFFECT, INDUCES AND IS INTERMIXED WITH A QUANTITY OF LOCAL SECONDARY AIR IN AT LEAST ONE INDUCTION UNIT LOCATED IN EACH ROOM, IN WHICH UNIT THE TEMPERATURE OF THE SECONDARY AIR BEFORE ITS MIXING WITH THE PRIMARY AIR IS TREATED IN HEATEXCHANGERS DISPOSED IN THE INDUCTION UNIT HAVING LIQUID HEAT-EXCHANGE MEDIUM SUPPLIED THERETO, THE LIQUID MEDIUM SUPPLIED TO THE EXCHANGER OF THE INDUCTION UNITS, IRRESPECTIVE OF THE OUTDOOR CONDITION AND THE SEASON, BEING AT A TEMPERATURE COMMON FOR SUBSTANTIALLY THE WHOLE PLANT, THE TEMPERATURE OF THE PRIMAR AIR BEING REGULATED IN ACCORDANCE WITH THE OUTDOOR CONDITION; THE IMPROVEMENT WHEREIN SAID COMMON TEMPERATURE OF THE LIQUID HEAT EXCHANGE MEDIUM IS CONTROLLED TO REMAIN IN A RANGE BELOW THE TEMPERATURE OF THE SECONDARY AIR, BUT NOT SUBSTANTIALLY BELOW THE DEW-POINT TEMPERATURE OF THE SECONDARY AIR, THE LIQUID MEDIUM THEREBY ABSORBING HEAT FROM THE SECONDARY AIR WITHOUT CASING CONDENSATION IN THE HEAT EXCHANGERS. 